DISEASE CHARACTERISTICS: Diagnosis of relapsed or refractory multiple myeloma confirmed by the presence of the following: Bone marrow plasmacytosis with at least 10 percent plasma cells Sheets of plasma cells OR Biopsy-proven plasmacytoma Documentation of at least one of the following criteria: Serum myeloma (M)-protein component at least 1.0 g/dL by serum protein electrophoresis Urine M-protein excretion more than 200 mg/24 hours by urine protein electrophoresis Stage IIA or IIIA disease Measurable disease The following are not considered measurable disease: Lytic bone lesions Anemia Bone marrow plasmacytosis Beta-2 microglobulin in serum Previously treated with conventional chemotherapy Progressing or relapsing disease at time of study